High-frequency machine transmitter



Aug. 25, 1931. I

W. HAHNEMANN' HIGH FREQUENCY MACHINE TRANSIITTER Filed Oct. 27, 1927Patented Au 25, 193i UNITED STATEST'PHA'TENT OFFICE WALTER TIAHNEMANN,OF BERLIN MARIENFELDE, GERMANY, A SSIGNOR TO 0. LORENZAKTIENGESELLSCHAFT, OF .BERLIN-TEMPELHOF, GERMANY HIGH-FREQUENCY MACHINETRANSMITTER Application filed Gctober 27, 1927, Serial No. 229,220,andin Germany October 28, 1926.

, -When using high-frequency machines in connection with frequencytransformers, particularly transformers of the iron-cored type, for theproduction of electric oscillating currents of high-frequency forwireless telegraphic ortelephonic purposes, one of the most essentialrequirements consists in that thefrequency of the currents produced bythe machine in accordance with its number of revolutions should be heldconstant to a. very high degree, as otherwise very minute variations ofthe speed of rotation, especially in the case of a very highmultiplication of the machine frequency being carried out, will cause ina heterodyne receiving apparatus cooperating with the transmittingsystem, corresponding variations of the pitch of the receiving beat noteso as to render practicable operation absolutely impossible. The recentdevelopment of speed regulators, however, especially a design of speedregulating devices operating according to the Well-known Tirrillprinciple, has made it possible to produce wireless waves by means ofelectric generators in connection with frequency raisers down to alength of 300 meters with suflicient constancy of frequency, whichhitherto has onlybeen accomplished by means of vacuum tubes.

Moreover, there exists a further drawback inherent to such machinetransmitters, especially when carrying out extremely highmultiplications, which practically presents itself as a trillingphenomenon of the beat note in the receiver. Such a trilling beat notewhich 'is characteristic of machine transmitters of the type inquestion, involves great disadvan 'tages especially when a receiver ofthe audion reaction type is employed, in that with a degree of reactioncomparatively much below that possible when receiving waves free of thistrilling disturbance such as of vacuum tube transmitters, the signalsare distorted to a large degree, the advantages of reaction in audionreceivers thus being decreased considerably. p r

. Theoretical analysis, as well as practical considerations andoscillographic investigations, have shown that the trilling phenomenonreferred to has its origin in minute frequency variations occurring inthe speed of not in absolute variations of the speed of rotation for,even with variations of the speed of 1/10.000 the forces of inertia areso large as not to produce practical disturbancesebut in frequencyvariations occurring between rotor and stator as the result of themechanical vibrations of the casing. These vibrations of the statorcasing and of its foundation possess a component in the direction aroundthe rotation axis presenting torsional oscillations around the same.They are caused to a great extent by the unequal forces which aretransferred by the rotation of the rotor,'whose crankshaft is neverabsolutely free of oscillating movements, to the casing acrss thebearings and impinging upon the latter to set it into oscillation. Thecasing,

therefore, is impinged upon once each revol-ution, thus performing anoscillating movement about its normal position. The phenomenonof thetrilling pitch of the beat note will now, after these preliminarystatements, be explained by the following consideration in'conne'ctionwith Figure 1 of the accompanying drawings, in which drawings:

Figure 1 is a schematic View of a highfrequency generator exponentiallyillustrating certain phenomenon pertaining tothep'roduction of heat notetrills.

Figures 2, 3 and 4 are similar views showing different ways of carryingthe'princip' le of the invention into practical effect.

Figure 5 is a diagram of a complete transmitting and receiving system asadapted for carrying out the invention. I

Supposing the circumference of rotor of the high frequency generator tobe c=2000 mm. (Figure 1), and amplitude of the component of rotation ofthe oscillations of the casing around the axis to be 8=1/10 mm. alongthis circumference, i. e., 28=2/l0 mm. to both sides from the normalposition, and supposing one torsional oscillation to occur once perrevolution of the rotor, a rise or decrease of frequency tions influencethe beat note of a heterodyne' receiver in that the beat note varies asmany times in one second by 100 oscillations, as correspoi ls to thenumber of revolutions of oscillations, of the machine per second. Thisphenomenon gives the impression of trilling of the beat note and will bedesignated as the trilling note of such a high-frequency machinetransmitter.

It is the object of the present invention to overcome the drawbacksoccurring in connection with the trilling note, for which the abovementioned ditlicult and laborious experimental work has furnished thenecessary analytical data and practical means. According to myinvention, means are provided for the machine which are adapted todecrease the vibrations of the stator casing around the rotation axis tosuch a minimum value as to reduce the frequency variations of themultiplied utilization frequency to a value practically insuiiicient togive rise to the phenomenon in question. The generic object to this endconsists in mechanically balancing the machine very accurately to adegree far above that hitherto known and required for ordinary purposes(for instance with respect to strains and stresses of material caused bypercussions ot' the machine structure), so that neither very minutepercussions giving rise to the trilling tone may occur or are damped toa practically unimportant value.

However there may occur cases, in which a trilling tone may not beeliminated even with a practically highest possible mechanical bmance ofthe machine, for instance when generating extra high frequencies, i. e.,employing extremely high multiplication ratios, or there may be caseswhere the costs of the plant play an essential part. In all such casesthe elimination or damping out of tor- '.sio11al oscillations around theaxis giving rise to the trilling note may be obtained to a less orgreater extent by additional means, as will be described hereinafter. Itwill be understood that the vibrations of the casing are not wholly orat all times caused by the vibrations of the rotor axis transferred tothe casing across the bearings, though this is by most the normal case,but any periodic percussions reaching the machine srructme from outside,for instance, trom a neighbouring machine, across a common foundationplate, may give rise to disturbances oi the sort in question.

In order to suppress the oscillating percussions of the casing of thealternating current generator G giving rise to the trilling note, I may,as shown in Fig. 2, connect with it a mechanical member or memberscoupled to it in such a way as to introduce a large damping and whichare preferably tuned to the frequency of the percussions. for example, adamping mass Q is schematically represented, the same consisting of areceptacle containing mercury and mechanically connected with the casingM of the machine. material presents the advantage in that mechanicalvibrations of small amplitude and large power may he damped by it in amost efiicient way. This mass of n'iercury may vary according toconditions but should be about 10% of the viln'ating mass of the highfrequency machine, in order to dampen the machine sufliciently toexclude trilling notes. In the calculation of the swinging massobviously only the upper portion of the machine, that is the housingwhich surrounds the rotor, need be taken into consideration, since thebed plate, which may be integral with the upper portion, is preventedfrom vibrating by its attachment to the usual foundation. This case issimilar to I rahms anti-rolling tanks for the prevention of the rollingmotion of ships.

According to a further object of my invention I connect with the casingin question a periodically moving, for instance, rotating member adaptedby virtue of the distribution of its masses and the periodicity of itsmovement, to act against the per-cussions oi the casing by compensation.For instance I may employ a balancing mass eccentrically rotating anddriven synchronous y with the rotor of the high-frequency machine bymeans of a suitable arrangement. Figure 3 represents schematically theembodiment of this teature of my invention, showing an eccentricallyrotating mass R mechanically connected to the casing of the machine.Thus while in Figure 2 an artificial decrease of ampli tude is effectedby damping means, in Figure 3 the oscillations of the casing aresuppressed by compensation.

The vibrations in question giving rise to the trilling note may befurthermore sup- The use of mercury as damping 1.11 Fig. 2,

pressed or minimized by suitably stiffening the machine. For instancethe machine frame or casing M may be connected to. its foundation plateby special stiffening rods S,

as shown in Fig. 4, or the base portion or portion M of the machineframe or casing below its horizontal center may be elongated to acertain degree with reference to its top portion or portion above itshorizontal center to increase the mass of the casing to the desireddegree In the illustration of the transmitting and I receiving systemshown in Fig. 5 the alternator G is shown as used to supply current to afrequency multiplier radiating energy to a heterodyne or regenerativereceiver. The signal frequency transmitted from the frequency multiplierand received by the recelver is imposed upon a carrier wave on,

which is also ordinarily impressed those frequency variations causedbymechanical vibration percussions produced by the action of thealternator and which in turn produce the beat note trills in thereceiver. By modimitting and receiving the messages while suppressingthose frequency variations mechanically produced and imposed by theaction of the alternator upon the carrier wave and which cause in thereceiver such beat note trills. c

In testimony whereof I have aflixed my signature.

WALTER HAHNEMANN.

fying the alternator as set forth such vibrations have been wholly orfor all practical purposes eliminated, with the result that thefrequencies causing beat note trills in the receiver are eliminated orsuppressed.

What I claim to be secured by Letters Patent of the United States is:

1. The method of transmitting messages between a wireless transmissionapparatus supplied with current by a high frequency alternatorand aheterodyne or regenerative receiver so as to prevent trilling of thebeat note in the receiver, which consists in transmitting and receivingthe messages while during transmission suppressing the mechanicaltorsional vibrations of the stator relative to therotor of thealternator which give rise to frequency variations producing such beatnote trills.

2. The method of transmitting messages between a wireless transmissionapparatus supplied with current by a high frequency alternator and'aheterodyne or regenerative stator relative to the rotor of saidalternator receiver so as to prevent trilling of the beat note in thereceiver, which consists in transmitting and receiving the messageswhile during transmission opposin a reslstance to the mechanicaltorsional v1 ratlons of the so as to suppress those vibrations whichgive rise to frequency variations producing such beat note trills.

3. The method of transmitting messages between a wireless transmittingapparatus supplied with current by a high frequency alternator and aheterodyne or regenerative receiver so as to prevent trilling of thebeat notes in the receiver, which consists in transmitting and receivingthe messages while suppressing those vibrations resulting from theaction of the alternator which give rise

